“I said you’re hurting me, I’m blind – and there’s no way he could not have seen my stick on the floor.

“I walk at a snail’s pace. They could have walked past me, driven past me in the van, or said ‘drop your weapon.’

“It’s a sad excuse. They wouldn’t even stop when I said I’m blind.

“I was absolutely terrified. I thought any second I’m going to have another stroke and this one will kill me.”

Mr Farmer’s horrific ordeal began at about 5.45pm on Friday.

He was walking along Peter Street, close to the Parmesan and Pepper restaurant, when police swooped.

Mr Farmer, who lives with his

18-year-old son, explained that as a result of having a stroke – which has left him registered blind – his brain “doesn’t believe the left exists” and he has trouble picking up objects on that side.

“The other day I walked into the back of a white van because it was parked and partly on the footpath,” he said. “Things can appear invisible.”

After the taser incident Mr Farmer was taken to Chorley Hospital for treatment and was later released.

He said the explanation police gave him for their actions was that they had received reports of someone wielding a Samurai sword wandering in Chorley.

“In your wildest dreams, you couldn’t mistake me for having a Samurai sword,” he said. “I didn’t just drop down in a helicopter. I’d walked a few hundred yards. They must have seen me.”

Mr Farmer, a former property developer and head of a large architectural practice in Chorley, said he was the founder of the City Living project.

Chief Superintendent Stuart Williams, who is responsible for policing in Chorley, said: “We received a number of reports that a man was walking through Chorley armed with a Samurai sword and patrols were sent to look for the man.

“One of the officers believed he had located the offender. Despite asking the man to stop, he failed to do so and the officer discharged his taser.

“It then became apparent this man was not the person we were looking for and officers attended to him straight away.

“He was taken Chorley Hospital by officers who stayed while he was checked over by medics. They then took him to meet his friends in Chorley at his request.

“Lancashire Constabulary deeply regrets what has happened. We have clearly put this man through a traumatic experience and we are extremely sorry.

“We have launched an urgent investigation to understand what lessons can be learned and the matter has also been referred to the Independent Police Complaints Commission.”